1. Field of the Invention
The present invention relates to an inspecting apparatus which is employed to inspect general performance of a photovoltaic devices, such as a photovoltaic cell, a photovoltaic string which is formed by connecting the photovoltaic cells in series, a photovoltaic devices panel which is formed by disposing a plurality of photovoltaic strings in parallel, and the like.
2. Description of the Background Art
It is well known that a silicon photovoltaic devices is employed to harness solar energy. In the manufacture of the photovoltaic devices, it is important to evaluate whether the photovoltaic devices has predetermined power generation capacity. The evaluation is usually performed by measuring output characteristics thereof.
The output characteristics is the photovoltaic conversion characteristics obtained by measuring current-voltage characteristics of photovoltaic devices under light irradiation. As a light source, it is desired to use the solar light. However, since the intensity of the solar light varies in relation to weather, a solar simulator is employed. In the solar simulator, a xenon lamp, a metal halide lamp or the like is employed as an alternative to the solar light. If the aforementioned light source has been lighted for a long time, the temperature thereof rises or the like, leading to a variation on the light intensity thereof. Therefore, by using the flash light of the aforementioned light source, it is able to plot the output characteristic curve of the photovoltaic devices on the basis of collected data with setting a voltage as the lateral axis and a current as the vertical axis (for example, refer to Japanese Patent Application Laid-Open No. 2007-88419).
The following different method from the solar simulator is disclosed in the Patent Document WO/2006/059615. By applying a voltage to a polycrystalline silicon photovoltaic devices element in a forward direction. The photovoltaic devices element emits electro-luminescence light (hereinafter referred to simply as a “EL light”). The photovoltaic devices element is inspected thereby. By studying the EL light emitted from the photovoltaic devices element, it is able to obtain the distribution of the current density of the photovoltaic devices element. The defects of the photovoltaic devices element can be found out on the basis of the uneven distribution of the current density. Namely, a portion which emits no EL light is decided to be a defective portion and the photovoltaic devices element can be decided to have the predetermined power generation capacity if the total area of the defective portions is smaller than a predetermined amount.
The structure of the inspecting apparatus described in the Patent Document WO/2006/059615 is schematically illustrated in FIG. 9. An inspecting apparatus 10 includes a darkroom 11, a CCD camera 12 which is disposed at an upper portion of the darkroom 11, a power source 14 which applies current to a photovoltaic cell 13 disposed on the floor of the darkroom 11, and an image processing apparatus 15 which processes image signals from the CCD camera 12.
The darkroom 11 is provided with a window 11a where a finder 12a of the CCD camera 12 is disposed. Therefore, an image to be photographed by the CCD camera 12 can be confirmed by watching with eyes from the finder 12a. As the image processing apparatus 15, a computer is employed.
In the inspecting apparatus 10 illustrated in FIG. 9, the photovoltaic devices cell 13 is disposed at a lower side of the darkroom 11 and is photographed by the camera from an upper side thereof. However, since the EL light emitted from the photovoltaic cell 13 is a weak light ray of wavelength between 1,000 nm and 1,300 nm, it is not able to be detected unless the photovoltaic cell is disposed inside the darkroom 11. In the case that the inspecting object is a piece of photovoltaic cell, the size thereof is about 100 mm×100 mm, which is possible to be disposed in a small-sized darkroom.
However, in the case that the inspecting object is a photovoltaic devices panel, the size thereof is about 2 m×1 m; therefore, the darkroom 11 has to have a dimension capable of disposing the photovoltaic devices panel. Further, the photovoltaic devices panel as the inspecting object has to be disposed inside the darkroom so as to be photographed by the CCD camera 12. Therefore, a door has to be provided in the darkroom so as to transport the photovoltaic devices panel into or carry out from the darkroom. If the inspecting apparatus is configured so as to transport the inspecting object into the darkroom, in the case that the disposed door is closed, shading effect has to be secured. It is also necessary that the inspecting apparatus is provided with a positing member and a guide member for transporting the photovoltaic devices in the darkroom of the inspecting apparatus. Furthermore, it is also necessary that the inspecting apparatus is provided with an electrifying means for applying a current to the photovoltaic devices in the darkroom. Thereby, the darkroom becomes complicated in structure and expensive in price.